Wall-rings of the above mentioned type, which form a single-piece structural component, require, on the one hand, a large storage space, and on the other, considerable transport volume, and are expensive to manufacture due to the complex tools required for injection-molding of the wall-rings, which consist, for example, of plastic.
The present invention is based on the objective of creating a wall-ring of the type described above, whose manufacture, due to the use of simple tools, is more cost-effective, and which requires less space during storage and transport. Inventively, this is achieved by the supporting frame being assembled from a plurality of frame elements by means of form or force-fitting connecting elements, and the circular connecting piece being formed by a plurality of circular segments arranged circumferentially one after the other, said circular segments being connected to each other and to the supporting frame by means of form and force-fitting connections.
In accordance with the present invention, it is particularly advantageous if the supporting frame is comprised of four frame elements, and the circular connecting pieces of at least eight elements, and preferably twelve segments, so that the segments result in a 45°, or in a 30° division, respectively, of the circular connecting piece. Here it is particularly advantageous if the supporting frame has a rectangular, in particular a quadratic circumferential contour with four corners and a central opening whereby four enlarged corner areas are formed, and the frame elements are formed by means of a division corresponding to the two diagonals that run through the corners.
The division of the supporting frame into individual frame elements and the division of the circular connecting piece into a plurality of circular segments allows for highly space-saving storage and small transport volume, because the individual segments can be combined into segment packages, and assembly of the inventive wall-ring does not take place until the axial fan has been installed. The inventive form and force-fitting connections of the individual elements, or of the segments, respectively, to and among each other, enables firstly, a simple assembly of the individual parts, and in addition a very robust connection that can hold the required holding forces.